What are the symptoms of a bad camshaft positioin sensor? I've been a chasing a rough idle on a 92 400E, 140k, for many months now (although I've not been driving it much). The car idles rough, shakes at idle, but only at idle, like bad motor mounts, but the motor mounts have been replaced. But when you drive the car it's smooth, can't tell anything is wrong with it. The reason I suspect the camshaft position sensor is 1) virtually everything else has been replaced and/or tested, and 2) disconnecting it has no impact - good or bad - on how the car runs. It's maybe a hundred dollar part so I guess I could just buy a new one and see what happens (as I did with all the other things that didn't fix it).

Does anyone know what the symptoms are for a bad camshaft position sensor or how it can be further tested? It's not putting off any fault codes.